Ultrasound is an important imaging modality for medical diagnostic purposes and as a guidance tool for diagnostic or therapeutic procedures, like soft tissue needle biopsy, tumor ablation, etc. Ultrasound can be used over the entire human body and has certain advantages over other modalities, including, among others: the ability to locate and characterize medical problems; lower cost compared to modalities such as MRI and CT; real time operation; and, the lack of ionizing radiation with the known associated health risks.
Ultrasound imaging systems transmit sound waves of very high-frequency (e.g., 1 MHz to 20 MHz) into the patient's body and the echoes scattered from structures in the patient's body are processed to create and display images and information related to these structures.
Ultrasound imaging can be applied to various regions or organs in the body. For example, a breast ultrasound procedure involves the placement of an ultrasound transducer over a region of interest of the breast with the radiologist or other medical professional (the “user”) viewing a real-time ultrasound image output on a display. The ultrasound machine monitor usually displays relevant text and/or graphical information next to the ultrasound image for simultaneous viewing by the user. The user can freeze a displayed image with medical findings of interest, and the corresponding image can be printed on a primer or stored in digital format.
2D free hand ultrasound imaging, the most common technique used today, represents a slice through the region of interest. 3D ultrasound scanning is available; however, it is usually used in conjunction with 2D scanning techniques. Currently, most diagnostic studies are performed using 2D scanning technique.
The vast majority of ultrasound guided biopsies and other invasive ultrasound guided invasive procedures done by free hand and other more automated modes use the ultrasound machine 2D display mode. Therefore, it is desirable to have a fast and accurate way to find the target during such invasive procedures.
It is important to accurately store positional annotations for later evaluation, since this is essential for final interpretation, diagnosis, and treatment. As digital storage and communication of medical information replace hard copy based storage and communication technologies, the accurate and consistent annotation of ultrasound and other medical images is critical. Correlation of ultrasound images with images of the same body region obtained with other modalities (MRI, CT, mammograms, PET, etc.) becomes increasingly important for medical diagnostic and therapeutic purposes. As a result, precise positional registration of the targets is important.
This importance is illustrated by noting that finding a small tumor can save a patient's life. The smaller the tumor is before treatment, the higher the probability of long term patient survival or cure; however, a small rumor is difficult to find in a patient's body and differentiate from other structures or artifacts in the same region. Many times a suspicious small finding can coexist is the same region with multiple benign findings (cysts, solid benign nodules, etc.) with similar appearance, which may create confusion during a follow up exam and may lead to missing the suspicious lesion. As imaging diagnostic devices provide ever greater detail and sub-millimeter resolution, accurate position registration and mapping of lesions is becoming increasingly important in order to take advantage of the increased capabilities.
Ultrasound procedures are highly dependent on the device users experience and training. Position recording of certain findings is important, especially for the small targets and/or multiple targets. Most frequently, an ultrasound user will hold the ultrasound transducer in one hand and use the other hand to operate the ultrasound machine controls. It is desirable to obtain the instant recording of target coordinates seen in the ultrasound image in relation to the anatomical reference (for example, a nipple) and the simultaneous recording of the transducer position. Currently, the automated recording of the transducer position in real time scanning is limited due to the motion of the pre-selected anatomical reference secondary to body and transducer induced motion. Therefore, it is desirable to continuously update the position of the anatomical references, or landmarks, and apply the correction to the obtained measurements.
The American College of Radiology (ACR) recommends that all ultrasound images be properly labeled. For example, for breast ultrasound images, the findings position, in clock face position, distance from Nipple C and ultrasound probe position and orientation should be displayed with the ultrasound images. Currently, ultrasound findings are manually labeled by an operator, which is time consuming and prone to errors. Manual labeling involves the typing of an approximate position in the organ or part of the body, since an accurate position registration is time consuming and, importantly, difficult for the user.
A significant shortcoming in ultrasound mapping is the reproduce-ability of target location from exam to exam. A patient's body position, including soft tissue which is subject to movement, with respect to the examination table and position guides, and the ability to track transducer location in a reproducible format are limiting factors in the accurate examination of a patient. This inaccuracy can lead to inaccurate diagnosis and, importantly, inaccurate lesion description is a comparative examination. This, in turn, leads to ambiguities in the ability to definitively gauge the growth of a lesion or, critically, the success of treatment.
There is need, therefore, for a sensor attachment for three dimensional ultrasound mapping that enables increased accuracy in positioning during ultrasound examination. The present invention provides such a device.